1. Field of the Invention
The present invention relates generally to a spray head air atomizing assembly and more specifically to an air atomizing assembly to control the flow of atomizing air in a fluid spray or other delivery device such as an air sprayer for spraying paints, adhesives, coatings, and other semi-liquid materials.
2. Description of the Prior Art
Two common types of spray or delivery devices exist for spraying or delivering a fluid to a substrate. One such device is a so-called airless type sprayer or delivery device in which an application fluid is forced through one or more nozzle openings at high pressure. With this type of device, the fluid is atomized or disbursed into tiny droplets as a result of the pressurized fluid passing through the nozzle opening.
A second such device is an air or air atomized spray gun or delivery device in which the application fluid passes through a nozzle orifice, at pressures usually much lower than the pressures employed with airless spraying, in combination with atomizing air flowing through a plurality of air orifices surrounding the nozzle opening. The atomizing air functions to atomize or disperse the application fluid after its exit from the nozzle opening.
Various airflow structures have been used in air spraying devices to supply the atomizing air to the application fluid stream. One of these includes a plurality of generally circular holes surrounding the application fluid nozzle opening and sloped to form a generally conical pattern so that the airstreams converge on the application fluid stream exiting the nozzle opening. Often these atomizing air streams are combined with additional air streams or horns at radially spaced positions which are designed to shape the atomized fluid stream.
Other airflow structures have included a nozzle tip having a plurality of external grooves in combination with a nozzle cap to define a plurality of fluid passages which converge in a spiral pattern toward the application fluid stream.
While many of the air atomizing assemblies of the prior art are generally acceptable when being used to atomize relatively low viscosity materials such as paint which are designed to be broken up and atomized easily, their performance is limited and less than satisfactory when used to atomize high viscosity materials (in excess of about 3,000 centipoises) and materials which have a high surface tension such as epoxies, urethanes, polyureas and other adhesives. These high viscosity and high surface tension materials are difficult to atomize and thus tend to “string” a lot as the application material travels from the spray nozzle to the substrate.
Accordingly, there is a need in the art for an improved air atomizing nozzle assembly, and more particularly a need for an air atomizing nozzle assembly which provides improved atomization of both conventional low viscosity materials such as paints as well as materials which have a relatively high viscosity and/or a high surface tension.